The use of ultrasound for the production of local hyperthermia in cancer treatment shows considerable promise. Various types of research ultrasound applicators are being tested, and some applicators are involved in patient treatment. Important in the evolution of ultrasound heating systems and in quality assurance and performance testing is the availability of phantoms which realistically portray the in vivo treatment situation. Both ultrasonic and thermal properties of tumors and the surrounding tissues must be adequately mimicked in phantoms. We have developed materials and methods which will allow us to construct such phantoms. This includes the important thermal (cooling) property of perfusion of blood through tissue. The major purpose of the proposed work is to develop a set of realistic perfusable phantoms for ultrasound hyperthermia. These phantoms will span a range from a relatively simple phantom possessing a spatially uniform perfusion rate to a complex phantom possessing spherical symmetry of the flow pattern with a spherical necrotic core being located at the center and a more highly perfused shell at its boundary. These phantoms will be made to be representative of the in vivo situation, but will also be geometrically simple enought to allow rigorous experimental testing of theoretical calculations of spatial and temporal temperature distributions. The above theoretical calculations involve rapid calculation of attenuated ultrasound beam intensity patterns and appropriate forms of the bioheat equation. Our group will also pursue this comparison between theory and experiment, first for a simple diathermy applicator and then for a more sophisticated annular ring transducer assembly for local deep heating. Quality assurance and performance phantoms are already under development in our lab, and this will promote early commercial availability of refinements in phantoms resulting from the work done in connection with this proposal.